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Pulmonary and Systemic Circulations Pulmonary circulation: –Path of blood from right ventricle through the lungs and back to the heart. Systemic circulation: –Oxygen-rich blood pumped to all organ systems to supply nutrients. Rate of blood flow through systemic circulation = flow rate through pulmonary circulation.

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Figure The circulatory plan in mammals and birds (Part 1)

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Figure The circulatory plan in mammals and birds (Part 2)

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Figure The circulatory plan in gill-breathing fish (Part 1)

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Figure The circulatory plans of some air-breathing fish (Part 1)

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Figure The circulatory plans of some air-breathing fish (Part 2)

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Figure The branchial vascular arches of a lungfish

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Figure The circulatory plan of squids and octopuses (Part 1)

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Figure Circulation through the body of a crayfish or lobster (Part 2)

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Box 23.3 Blood flow through the tissues of an insect is principally through lacunae and sinuses

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Refractory Periods Refractory periods: Heart contracts as syncytium. Contraction lasts almost 300 msec. Refractory periods last almost as long as contraction. Myocardial muscle cannot be stimulated to contract again until it has relaxed. –Summation cannot occur.

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Electrocardiogram (ECG/EKG) EKG (ECG) The body is a good conductor of electricity. –Tissue fluids have a high [ions] that move in response to potential differences. Electrocardiogram: –Measure of the electrical activity of the heart per unit time. Potential differences generated by heart are conducted to body surface where they can be recorded on electrodes on the skin. Does NOT measure the flow of blood through the heart.

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ECG Leads ECG leads Bipolar leads: –Record voltage between electrodes placed on wrists and legs. –Right leg is ground. Unipolar leads: –Voltage is recorded between a single “exploratory electrode” placed on body and an electrode built into the electrocardiograph. –Placed on right arm, left arm, left leg, and chest. Allow to view the changing pattern of electrical activity from different perspectives.

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Figure 23.4 The conducting system and the process of conduction in the mammalian heart (Part 1)

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Figure 23.4 The conducting system and the process of conduction in the mammalian heart (Part 2)

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Figure 23.4 The conducting system and the process of conduction in the mammalian heart (Part 3)

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Circulatory adjustment during dives Bradycardia –Drop in cardiac output –Weddell seals show an 86% drop in cardiac work and an 85% reduction in blood flow to their ventricular heart muscle Regional vasoconstriction –Becomes a “heart-lung-brain” machine –Large concentration of rbcs in their blood when they are diving –Rbcs stored in their spleen- release during dive

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Metabolism during dives 3 factors determine the limits of endurance of the O 2 –dependent tissues –Magnitude of O2 store available –Rate of use of the O2 store –Extent to which P02 can fall before impairing the function of O 2 -dependent tissues MR during dive is the most important factor in determining metabolic limits on dive duration –low MR, slow O 2 depletion, and slow lactic acid accumulation

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The aerobic dive limit Prolong dive has major behavioral consequences –Requires time for ridding body of lactic acid –Must stay at the water’s surface where it can breathe –Lactic acid burdens of successive dives Additive Example- a seal that accumulates 80 ml lactic acid/ 100 ml of blood has to remain at the surface over an hour to return its lactic acid to resting level

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Decompression sickness (DS) Caused by N 2 absorption from a compressed-air source –Start of dive– tissue contains a [N2] DS occur after a long deep dive and then surfaces suddenly –PN 2 pressure falls in the lungs to its ordinary value –N2-charged blood and other tissues start to lose N2 in the lung air –Bubbles of blood may form within the blood and tissues

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Decompression sickness (DS) 2 Breath-hold dives must be repeated many times to cause DS in humans Marine animals avoid DS during deep dives by alveolar collapse –Special features of lungs and thorax Keep pulmonary N 2 within lungs Avoid build up in blood and tissues Lung air moves to conducting airways